This Mentored Research Scientist Development Award will allow the candidate to pursue her research and training goals at the University of California, San Diego and Pro-COMUSIDA, a community health clinic in Tijuana, Mexico. The candidate's long-term career goal is to become a leader in the area of international HIV prevention. She aims to develop a base of skills and knowledge necessary to facilitate her transition into an independent investigator. Her specific training objectives are to: 1) develop a thorough understanding of individual- and dyad-level factors that contribute to HIV risk among couples with particular emphasis on drug use, sexual relationship power, and intimate partner violence;2) gain proficiency in research design and statistical techniques necessary for conducting dyad-level analyses with couples;3) acquire an in-depth understanding of theory-based HIV prevention interventions in order to design a couples-based HIV prevention intervention for female sex workers (FSWs) and their regular sexual partners;4) obtain further training in the ethical conduct of research, particularly with unique populations such as FSWs;and 5) to build general skills for an academic career. Recently, HIV prevalence among FSWs in Tijuana has increased from 2% to 6%, and 14% among FSW who inject drugs (FSW-IDUs). Globally, FSWs are considered a "bridge" population who may transmit HIV/STIs to the general population. While the majority of research thus far has focused on individual-level risk factors among FSWs, comparatively little is known about their sexual partners and relationship characteristics. To address these gaps in knowledge, the proposed cross-sectional study will utilize quantitative methods to examine individual- and dyad-level correlates of HIV drug- and sex-risk behaviors among FSWs and their regular sexual partners in Tijuana.